On the 11th of this month, the US public will remember those who fell on that fateful day six years ago. The nation will also be remembering the thousands more who have fallen since, in the name of defeating the perpetrators of September 11. While in past years that 'sacrifice' was accepted by a great many Americans, this year's anniversary, particularly, will be observed in the dark shadow of the nightmare that has become Iraq.
The Iraq policy - establishing a stable and viable democracy in that country - emerged as a vital part of the Bush administration's post-September 11 agenda. Four years on from the invasion, however, that policy has created the possibility of al-Qaeda claiming a major victory: US withdrawal from Iraq in circumstances of total failure.
The planning for the 2003 war concentrated on the conflict, not on the subsequent rebuilding of Iraq. It was predicated on the assumption that toppling Saddam Hussein would be a difficult and casualty-intensive endeavour but that, once he was deposed, the situation would quickly revert to normal.
This assumption was based on 'dictator logic' - that dictators care only about staying in power, not what will happen once they're gone - and an absurdly simplistic view that, once the dictator fell, all of Iraq would quickly accept the new regime.
Compounding the lack of planning and resource allocation, the US immediately removed all those connected with the previous regime. This not only created a skills vacuum, but also drove many people into the growing insurgency.
When all is said and done, the bill for post-September 11 operations in Iraq and Afghanistan alone will exceed US$1 trillion: yet both states, and especially Iraq, will remain in turmoil, as strongholds for radical Islamist terrorists. When added to the huge and rising US death toll in Iraq - the total stood at 3,739 troops as of Saturday, with a further 298 coalition allies dead - plus the thousands of seriously wounded, Iraq has become an unmitigated disaster.
The record of the 'war on terror' is by no means all negative. There have been a number of successes against al-Qaeda: the US-led action in Afghanistan has denied the group an operating base. As a consequence, it must function on a smaller and less adventurous scale, from the shadows.